Tandem electrical control

ABSTRACT

A tandem electrical control is provided comprising a plurality of housing sections and wherein two base assemblies are rigidly secured to the same housing section. Coupling straps disposed in channels in the housing sections maintain the control in assembled relationship. An outer tubular shaft for adjusting some of the sections independently of others adjusted by an inner shaft is secured to the inner shaft by means of a C washer abutting a bushing and extending through a groove in the wall of the outer tubular shaft into a reduced diameter portion of the inner shaft. Rattling between the two shafts is eliminated by disposing a portion of a tubular shaft of an actuator between the two shafts. Actuators that are to be simultaneously adjusted have coupling means in the form of driving lugs projecting from one of the actuators engaging lug receiving notches in another. One of the driving lugs is larger than the other to precisely orient the actuator and enable assembly in only one position.

United States Patent [1.91

Van Benthuysen et a1.

[451 July 17, 1973 TANDEM ELECTRICAL CONTROL [751 Inventors: John D. Van Benthuysen; Wilbert N. Budd, both of Elkhart, Ind.; Robert E. Cormican, Cherokee Village, Ark.

[73] Assignee: CTS Corporation, Elkhart, Ind.

[22] Filed: Sept. 16, 1970 [21] Appl. No.: 80,520

[52] U.S. C1. 338/134 [51] Int. Cl 1101c 5/00 [58] Field of Search 338/128-134, 184

[56] References Cited UNITED STATES PATENTS 3,611,245 10/1971 Puerner 338/134 2,781,436 2/1957 Barden 338/134 X 2,971,174 2/1961 Lyon 338/130 2,257,979 10/1941 Rubinstein.... 338/132 X 2,628,298 2/1953 Budd 338/134 2,659,793 11/1953 Daily et al. 338/134 2,777,924 1/1957 Youngbeck... 338/134 2,941,175 6/1960 Zarrillo 338/134 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Stanley J. Witkowski Attorney-John J. Gaydos et a1.

[5 7 ABSTRACT A tandem electrical control is provided comprising a plurality of housing sections and wherein two base assemblies are rigidly secured to the same housing section. Coupling straps disposed in channels in the housing sections maintain the control in assembled relation-' tion of a tubular shaftof an actuator between the two shafts. Actuators that are to be simultaneously adjusted have coupling means in the form of driving lugs projecting from one of the actuators engaging lug receiving notches in another. One of the driving lugs is larger than the other to precisely orient the actuator and enable assembly in only one position.

17 Claims, 5 Drawing Figures liq-seat:

PATE-NTEU JUL 1 1 ms FIGURE-3 FIGURE-4 INVENTORS JOHN D. VAN BENTHUYSEN WILBERT H.

l IM I FIGURE'I FIGURE-5 BUDD CORMICAN TANDEM ELECTRICAL CONTROL The present invention relates to electrical controls and, more particularly, to at least a pair of controls connected in tandem.

In the past it has been found desirable to utilize tandem controls for systems utilizing stereophonic principles having two or more separate amplifier speaker systems or channels in order that the tandem controls can be adjusted together to bring about identical variations in the different channels. Such controls are customarily made by fabricating two similar variable resistance devices, arranging them in tandem, and connecting the devices to one another so that the two may be mounted as a single unit. In order to bring about an identical variation in the controls it is necessary to identically position each of the resistance elements making up the controls. Where each of the controls is separately fabricated before being arranged in tandem, a mounting plate or similar device has been utilized to join the two controls together. Due to standard manufacturing tolerances it is extremely difficult to position the two resistance elements in the separate controls so as to bring about identical variations upon rotation of the shaft actuating the controls. Accordingly it would be desirable to fabricate a tandem electrical control wherein the two resistance elements are precisely registered with respect to one another and constrained against movement relative to one another.

Ordinarily controls of this type are provided with a bushing such that the control can be mounted to a panel. The control is provided with an inner shaft and a tubular outer shaft mounted for rotation relative to one another. Any severe blow or force applied to the shaft is transmitted through the shaft to the actuators or drivers attached thereto often causing damage to the driver or to the connection between the driver and shaft. Accordingly it would be desirable to transmit forces applied to the shafts to the bushing and panel thereby eliminating damage to the working parts of the control.

In tandem control constructions having an inner shaft rotatable within a tubular shaft the bushing adjacent the mounting plate of the rear control rotatably supportsthe shafts. Sufficient clearance must be provided between the inner and outer shafts to prevent binding therebetween resulting from slight coaxial misalignment due to manufacturing tolerances when the controls are assembled together. Such-clearance between the shafts causes the inner shaft to vibrate and contact the outer shaft. In the past, various means have been devised for eliminating the vibration of the inner shaft or at least for damping the vibrations to the extent that they no longer create objectionable rattle. Examples of such means being disclosed in the patents to Barden U.S. Pat. No. 2,781,436 issued Feb. 12, 1957, and Leufling et al. U.S. Pat. No. 3,256,713 issued June 21, 1966, both patents being assigned to the-assignee of the present invention. Although these prior art devices provide solutions for eliminating or damping rattle, it would be desirable to provide improved means for eliminating rattle between the inner shaft and outer tubular shaft of a tandem electrical control by disposing a tubular portion of an actuator therebetween.

lnorder to bring about an identical variation in the adjustment of the tandem electrical control, it is necessary to position each of the contactors with respect to their respective resistance elements such that rotation of the shaft accurately positions each contactor in the same position as the other. Therefore in addition to precisely registering the base assemblies it is necessary to precisely register the contactors and their actuators. In the past in providing for a driving connection between the two-contactors, one solution has been to provide driving lugs projecting forwardly from one section of a tubular outer shaft of one driver and projecting into rearwardly opening notches in the other driver as shown in Budd et al. U.S. Pat. No. 2,883,500 assigned to the same assignee as the present invention. In such a construction it would be possible to rotate the connection 180 out of phase and still have a driving connection thus destroying the ability to identically vary the controls upon rotation of the shaft. Accordingly it would be desirable to fabricate a tandem electrical control wherein the two actuators are accurately positioned with respect to one another and can be assembled in only one position.

Since one of the shafts of the electrical control will extend through several of the individual sections of the control, it is necessary to accurately position each section with respect to the others such that binding or restraining forces will not be applied to the shaft extending therethrough. In the past this objective has been achieved by fastening tangs or tabs projecting forwardly from the wall of the cover of one control through slots'in the rear wall of the next forward control and deforming them to secure the two controls together. Such a construction renders it difficult to accurately position the two individual controls relative to one another and also multiplies the possibility of deviation as additional units are added to the tandem control. Accordingly it would be desirable to fabricate a tandem electrical control wherein the individual housing sections are accurately positioned relative to one another by means of coupling straps extending the length of the tandem electrical control such that various numbers of contrls can be assembled together by simply changing the length of the coupling straps without affecting the registration of each controlrelative to another.

Accordingly it is an object of the present invention to provide an improved tandem electrical control. Another object of the present invention is to provide a tandem electrical control wherein two stereo bases are secured to the same molded housing. An additional object of the present invention is to provide a tandem electrical control wherein the driver shafts are rotatably secured in a bushing of the control whereby forces applied to the shafts are transmitted to the bushing. A further object of the present invention is to provide a tandem electrical control wherein rattle between the shafts of the control is eliminated without interfering with the freedom to independently adjust each shaft. Yet another object of the present invention is to provide a tandem electrical control wherein the actuators terizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly, the present invention is concerned with a tandem electrical control wherein two sections of the tandem control can be adjusted together to bring about identical variations in their corresponding circuits. In the preferred embodiment of the present invention two base assemblies are rigidly secured to one housing section. A plurality of housing sections is secured together by means of a pair of coupling straps extending the length of the control having a split end deformed to secure the control together. An outer tubular shaft for adjusting some of the sections independently of others adjusted by an inner shaft is secured to the inner shaft by means of a C washer abutting a bushing extending through a groove in the wall of the outer tubular shaft into a reduced diameter portion of the inner shaft. The actuators that are to be adjusted together have coupling means in the form of driving lugs projecting from one of the actuators engaging lug receiving notches in the other. One of the driving lugs is larger than the other whereby the actuators can be assembled in only one position..A portion of a tubular shaft of one of the actuators is disposed between the inner shaft and the outer tubular shaft to prevent rattle therebetween.

For a better understanding of the present invention reference may be had to the accompanying drawings wherein the same reference numerals have been applied to like parts and wherein: FIG. 1 is an isometric view of an improved tandem electrical control built in accord with the present invention; FIG. 2 is an enlarged sectional view of the control shown in FIG. 1 with parts broken away; FIG. 3 is an enlarged partially exploded view of the control shown in FIG. 1 with some parts rotated to show features of the present invention; FIG. 4 is an enlarged view of a housing section of the control shown in FIG. 1; and FIG. 5 is an enlarged sectional view taken along lines VV of FIG. 2 assuming FIG. 2 to be shown in full.

As best shown in FIG. 1 a tandem electrical control comprises a plurality of housing sections 11, l2, l3, 14, each of said sections being preferably molded from a suitable plastic material. Disposed adjacent the housing sections 11 a mounting plate 16 is secured to a threaded bushing 17 for rotatably supporting an inner shaft 18 and an outer tubular shaft 19 and for mounting the control 10 to a not shown panel. Each of said housing sections 11, 12, 13, 14 is provided with diametrically opposed channels 21 for receiving channel engaging means in the form of a pair of coupling straps 22 passing through slots 23 in the mounting plate 16. The coupling straps each have a headed portion 24 engaging the mounting plate 16 adjacent the slots 23 and are provided with split ends 26 which are spread apart to secure the housing sections ll, 12, 13, 14 together.

The first housing section I] is provided with registration means comprising a plurality of tabs 27 for regis tering a pair of base assemblies 28, 29 at opposite ends assemblies 28, 29 to the first housing section 11, the bases 31 are provided with a plurality of notches 37 disposed about the periphery of the base for cooperation with the tabs 27 extending from the housing section 11. Once the base assemblies 28, 29 have been positioned in place, the tabs 27 are heat swaged over the bases 31 at 30 to rigidly secure the bases 31 thereto/Thus the two resistance elements 32 secured to the two bases 31 are identically registered in spaced parallel relationship.

A contactor assembly 38 comprising an actuator or driver 39 having a contactor 41 secured thereto is positioned in the first housing section 11 engaging one of the resistance elements 32 and a second contactor assembly 38 is positioned in the second housing section 12 for engaging the other resistance element 32. The two actuators 39 are provided with a driving connection in order to insure that the two contactors 41 rotate together for bringing about identical variation in the resistance upon rotation of one of the shafts. As shown in FIG. 2 and 3 the actuator 39 disposed in the second housing section 12 has a tubular portion 40 extending along the outer tubular shaft 19 terminating in a pair of diametrically opposed lugs 42, only one of which is shown, interfitting in a pair of lug receiving notches 43 disposed adjacent the outer tubular shaft 19 in the actuator 39 positioned in the first housing section 11. An alternative connection is shown in FIG. 2 between actuators 39 in the housing sections 13 and 14 wherein lugs 42, only one of which is shown, project from the actuator 39 disposed in the thrid housing section 13 into mating engagement with lug receiving notches 43 in a tubular portion 45 of the actuator 39 disposed in the fourth housing section 14. In order to insure that the actuators 39 are properly positioned, one of the driving lugs 42 is larger than the other thereby insuring entry into the lug receiving notches 43 in only one position. This eliminates the problems associated with assembly out of phase occurring with symmetrical configurations. Each of the actuators 39 is provided with a thrust bearing 44 engaging an annular ring 46 projecting inwardly from a wall of the housing sections 11, 12, 13, 14. For the purpose of limiting the amount of rotation of the actuator 39, the actuator 39 is provided with a stop member 47 integrally formed on the rear face thereof for engaging a stop 48 in one of the housing sections ll, 12, 13, 14. In order to distribute the force required to stop rotation of the shafts each of the housing sections 11, 12, 13, 14 can be provided with a stop 48 engaging a stop member 47 on its respective actuator 39.

As best shown in FIG. 2 the actuator 39 positioned in the first housing section 11 has a tubular shaft portion 49 extending axially along the inner shaft 18 between the inner shaft 18 and the outer tubular shaft 19, This eliminates rattle between the outer tubular shaft 19 and inner shaft 18. The tubular outer shaft 19 is shorter on one side than the other to provide driving connection with the actuator 39 positioned in the first housing section 11 having a similar configuration.

In order to eliminate transmission of forces applied to the inner shaft 18 and the outer tubular shaft 19 to the internal working parts of the control 10, a C washer 51 is positioned against the bushing 17. As best shown in FIGS. 2 and 3, the inner shaft 18 is provided with a reduced diameter portion 52 and the outer tubular shaft 19 is provided with a circumferential groove 53 extending through portions of the outer tubular shaft 19 at diametrically opposed locations 54, only one of which is shown in FIG. 3. The legs of the C washer 51 extend through the outer tubular shaft at 54 into the reduced diameter portion 52 of inner shaft 18 thereby securing the outer tubular shaft 19 against axial displacement relative to the inner shaft 18. Thus forces applied to the shafts are transmitted through the C washer 51 to the bushing 17 and absorbed by the panel mounting the control 10.

According to the preferred embodiment of the present invention four housing sections ll, 12, 13, 14 are employed with the third housing section 13 securing a pair of base assemblies 56, 57 in the same manner as the first housing section 1 1. As best shown in FIG. 3 the housing sections 12 and 14 are provided with a plurality of relieved areas 35 in alignment with the tabs 27 to provide sufficient space for the tabs 27 after they have been swaged. In order to secure an actuator 39 positioned in the third housing section 13 to the inner shaft 18, the inner shaft 18 is provided at the end thereof with a pair of opposed notches 58 corresponding to a pair of shoulders 59 extending inwardly from the actuator 39. A flat 61 at the end of the inner shaft 18 mates with a not shown flat on the actuator 39 in the third housing section 13 to insure rotation of the actuator 39 upon rotation of the inner shaft 18.

While there has been illustrated and described what is at present considered to be a preferred embodiment of the present invention, it will be appreciated that numerous changes and modifications are likely to occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

I 1. An electrical control having an inner shaft and a tubular outer shaft, a housing, a bearing mounted in the housing and rotatably supporting said shafts, and a washer abutting said bearing and positioning said outer shaft axially on said inner shaft for constraining relative axial movement between said shafts whereby forces applied to said shafts are transmitted to said bearing through said washer.

2. The electrical control of Claim 1 wherein said tubular outer shaft is provided with a groove intermediate the ends thereof and with a slot extending through a portion of said tubular outer shaft, said washer being positioned in said groove and extending through the slot into engagement with the inner shaft.

3. The electrical control of claim 2 wherein said inner shaft is provided with a reduced diameter portion and said washer extends through the slot in said tubular outer shaft into said reduced diameter portion.

4. The electrical control of claim 2 wherein said tubular outer shaft is provided with a plurality of slots, said washer extending through said plurality of slots into engagement with the inner shaft.

5. The electrical control of claim 2 wherein said groove communicates with said slot.

6. A tandem electrical control comprising first and second housing sections, a pair of base assemblies each comprising a base and a resistance element, said first housing section having registration means for registering said pair of base assemblies in spaced relationship and substantially constraining said pair of base assemblies against movement relative to one another, a contactor assembly positioned in each of said first and second housing sections for wipably engaging said base assemblies, and a shaft rotatably supported by said control, said shaft constraining said contactorassemblies to rotate therewith.

7. The tandem electrical control of claim 6 wherein said registration means comprises a plurality of tabs interfitting with a plurality of notches in said bases.

8. The tandem electrical control of claim 7 wherein the ends of said tabs are deformed over said bases to securely fasten said pair of base assemblies to said first housing section.

9. The tandem electrical control of claim 6 wherein said housing sections are provided with diametrically opposed channels, and channel engaging means disposed in said channels secure said housing sections together.

10. The tandem electrical control of claim 6 wherein one of said contactor assemblies is provided with driving lugs and the other is provided with lug receiving notches whereby said contactor assemblies are constrained to rotate together.

11. The tandem electrical control of claim 6 wherein third and fourth housing sections are provided, a second pair of base assemblies is provided each comprising a base and a resistance element, said third housing section having registration means for registering said second pair of base assemblies in spaced relationship and substantially constraining said second pair of base assemblies against movement relative to one another, a contactor assembly positioned in each of said third and fourth housing sections, and a tubular outer shaft positioned over said shaft whereby said contactor assemblies positioned in said third and fourth housing sections can be actuated independently of the contactor assemblies positioned in said first and second housing sections.

12. The tandem electrical control of claim 11 wherein a threaded bushing rotatably supports said shafts, and a washer abutting said bushing positions said outer shaft axially on said inner shaft whereby forces applied to said shafts are transmitted to said bushing through said washer.

13. The tandem electrical control of claim 11 wherein one of said contactor assemblies comprises an actuator having a tubular portion disposed between said inner shaft and said tubular outer shaft thereby preventing vibration of the inner shaft against the outer shaft.

14. A tandem electrical control comprising a housing, a pair of base assemblies, a shaft rotatably supported in said housing, a first contactor assembly constrained to rotate upon rotation of said shaft for wipably engaging one of the base assemblies of said tandem electrical control, and a second contactor assembly constrained to rotate upon rotation of said first contactor assembly for wipably engaging another of the base assemblies of said tandem electrical control, one of said first and second contactor assemblies being provided with a plurality of driving lugs and the other being provided with a plurality of lug receiving notches, said lugs and said notches being spaced so as to permit mating in only one position.

15. The control of claim 14 wherein the matingin only one position is achieved by one of the plurality of driving lugs being larger than the other driving lugs.

said slots.

17. The tandem electrical control of claim 15 wherein said channel engaging means has split ends folded apart in opposite directions engaging one of said housing sections and cooperating with the portion of vsaid channel engaging means abutting against said mounting plate to secure said plurality of housing sections together. 

1. An electrical control having an inner shaft and a tubular outer shaft, a housing, a bearing mounted in the housing and rotatably supporting said shafts, and a washer abutting said bearing and positioning said outer shaft axially on said inner shaft for constraining relative axial movement between said shafts whereby forces applied to said shafts are transmitted to said bearing through said washer.
 2. The electrical control of Claim 1 wherein said tubular outer shaft is provided with a groove intermediate the ends thereof and with a slot extending through a portion of said tubular outer shaft, said washer being positioned in said groove and extending through the slot into engagement with the inner shaft.
 3. The electrical control of claim 2 wherein said inner shaft is provided with a reduced diameter portion and said washer extends through the slot in said tubular outer shaft into said reduced diameter portion.
 4. The electrical control of claim 2 wherein said tubular outer shaft is provided with a plurality of slots, said washer extending through said plurality of slots into engagement with the inner shaft.
 5. The electrical control of claim 2 wherein said groove communicates with said slot.
 6. A tandem electrical control comprising first and second housing sections, a pair of base assemblies each comprising a base and a resistance element, said first housing section having registration means for registering said pair of base assemblies in spaced relationship and substantially constraining said pair of base assemblies against movement relative to one another, a contactor assembly positioned in each of said first and second housing sections for wipably engaging said base assemblies, and a shaft rotatably supported by said control, said shaft constraining said contactor assemblies to rotate therewith.
 7. The tandem electrical control of claim 6 wherein said registration means comprises a plurality of tabs interfitting with a plurality of notches in said bases.
 8. The tandem electrical control of claim 7 wherein the ends of said tabs are deformed over said bases to securely fasten said pair of base assemblies to said first housing section.
 9. The tandem electrical control of claim 6 wherein said housing sections are provided with diametrically opposed channels, and channel engaging means disposed in said channels secure said housing sections together.
 10. The tandem electrical control of claim 6 wherein one of said contactor assemblies is provided with driving lugs and the other is provided with lug receiving notches whereby said contactor assemblies are constrained to rotate together.
 11. The tandem electrical control of claim 6 wherein third and fourth housing sections are provided, a second pair of base assemblies is provided each comprising a base and a resistance element, said third housing section having registration means for registering said second pair of base assemblies in spaced relationship and substantially constraining said second pair of base assemblies against movement relative to one another, a contactor assembly positioned in each of said third and fourth housing sections, and a tubular outer shaft positioned over said shaft whereby said contactor assemblies positioned in said third and fourth housing sections can be actuated independently of the contactor assemblies positioned in said first and second housing sections.
 12. The tandem electrical control of claim 11 wherein a threaded bushing rotatably supports said shafts, and a washer abutting said bushing positions said outer shaft axially on said inner shaft whereby forces applied to said shafts are transmitted to said bushing through said washer.
 13. The tandem electrical control of claim 11 wherein one of said contactor assemblies comprises an actuator having a tubular portion disposed between said inner shaft and said tubular outer shaft thereby preventing vibration of the inner shaft against the outer shaft.
 14. A tandem electrical control comprising a housing, a pair of base assemblies, a shaft rotatably supported in said housing, a first contactor assembly constrained to rotate upon rotation of said shaft for wipably engaging one of the base assemblies of said tandem electrical control, and a second contactor assembly constrained to rotate upon rotation of said first contactor assembly for wipably engaging another of the base assemblies of said tandem electrical control, one of said first and second contactor assemblies being provided with a plurality of driving lugs and the other being provided with a plurality of lug receiving notches, said lugs and said notches being spaced so as to permit mating in only one position.
 15. The control of claim 14 wherein the mating in only one position is achieved by one of the plurality of driving lugs being larger than the other driving lugs.
 16. A tandem electrical control comprising a plurality of housing sections, each of said sections being provided with diametrically opposed channels, channel engaging means disposed in said channels for securing said housing sections together, and a mounting plate disposed adjacent one of said housing sections, said mounting plate being provided with a pair of diametrically opposed slots and said channel engaging means being disposed in said diametrically opposed slots with a portion thereof engaging the mounting plate adjacent said slots.
 17. The tandem electrical control of claim 15 wherein said channel engaging means has split ends folded apart in opposite directions engaging one of said housing sections and cooperating with the portion of said channel engaging means abutting against said mounting plate to secure said plurality of housing sections together. 